Thanks for your replies Aghadowey, especially for finding Catherine Mary on the Irish Genealogy civil records website.It's more than I was able to do!
So, 3 sisters, all alive and all called Mary! Pretty darn unusual,if you ask me!!
Neither was I able to find a record for the first born sibling, James Joseph, in 1903, on the Irish Genealogy civil records website.I am going to have another look now using the surnames Spullen, Spallen etc in case of another incorrect indexing,but if you can locate it I would be very grateful.
Thanks again.